hamming: Sync tests

[tasxatzial]

The current tests were returning nil for strands of unequal length. Admittedly, nil is one of the trickiest parts of the language, but this looks like an incorrect use of nil to me. I've replaced them with Exceptions but will revert if there's any disagreement.

[github-actions]

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[ErikSchierboom]

I think an exception makes more sense